When a heart valve of a human body does not normally work, causing embarrassments as constriction of the opening of the heart valve and reflux of blood, the heart valve must be replaced by a substitute valve. As the substitute valve presently used, mention may be made of a mechanical valve formed of a artificial material, a xenogenic bioprosthetic valve taken from an animal such as a pig, and an allogeneic bioprosthetic valve donated from another human body, etc. These valves have the following problems. Although the mechanical valve is durable, the recipient must take an anticoagulant for the entire lifetime. On the other hand, in the xenogenic bioprosthetic valve, the recipient needs not to take an anticoagulant for the lifetime; however deposition of calcium and the like takes place for a long time, causing malfunction in the valve, with the result that the valve must be exchanged with a new substitute valve at an interval of about 15 years. Furthermore, in the case of the allogeneic bioprosthetic valve, because the number of donors is limited, a sufficiently large number of allogeneic bioprosthetic valves are not easily obtained.
Of them, the xenogenic bioprosthetic valve is prospective for the reasons that a sufficient number of valves can be provided and patients are not necessary to take an anticoagulant for their lifetime after transplant. Therefore, the xenogenic bioprosthetic valve is expected to be more useful than other substitute valves only if the drawback of poor durability is overcome.
In the context, the following method is known which suppresses the post-transplant immunological rejection and improves the durability of a xenogenic bioprosthetic valve taken from an animal such as a pig (for example, see Japanese Publication No. 6-261933). In this method, a xenogenic bioprosthetic valve is first immersed in a cell-removing solution such as bile acid or a surfactant, thereby removing cells originated from the animal such as endothelial cells and fibroblast cells (cell-removing process). Then, the xenogenic bioprosthetic valve from which original cells have been removed is immersed in a cell-containing solution containing autologous cells, such as endothelial cells and fibroblast cells, taken from a recipient human body (to which the xenogenic bioprosthetic valve is to be transplanted), thereby seeding the autologous cells in the xenogenic bioprosthetic valve (cell-seeding process).
However, in the processing method mentioned above, since a xenogenic bioprosthetic valve taken from an animal cannot be efficiently treated in the cell-removing process and cell-seeding process, the resultant xenogenic bioprosthetic valve fails to acquire sufficient biocompatibility. In other words, since original cells more or less remain in the cell-removing process, the biocompatibility of the resultant xenogenic bioprosthetic valve decreases due to the presence of the original cells.
In these circumstances, the this inventors have intensively conducted experimental studies with the view toward over coming the aforementioned problems. They devised a method of supplying the cell-removing solution for immersing a xenogenic bioprosthetic valve at a flow rate virtually corresponding to the human blood flow and/or irradiating the xenogenic bioprosthetic valve immersed in the cell-removing solution with microwave. As a result, they found that the number of remaining original cells significantly decreases by this method.